This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Dengue viruses are the most common cause of mosquito-borne viral disease in tropical and subtropical regions around the world. Although it is no longer endemic to the United States, sporadic cases do occur and epidemics are increasingly common in the Caribbean and along the southern border of the U.S. Antibody produced during dengue virus infection provides homotypic immunity. However, pre-existing, circulating antibodies can produce a non-protective antibody response that can intensify the course of disease in a subsequent heterotypic infection. Theoretically, an attenuated live virus or whole protein vaccine could lead to severe disease during a post-vaccination primary infection. An understanding of this antibody dependent enhancement phenomenon, as it occurs in humans, is critical to the development of vaccines that will provide long-term protection without increasing the risk of dengue hemorrhagic fever (DHF). To date, most published anti-dengue monoclonal antibodies (MAbs) are of mouse origin. However, mice are neither normal hosts for dengue virus nor do they develop severe infection, such as DHF, after inoculation. Therefore, these reagents may not reflect the repertoire and roles of antibody produced by humans during natural infection. Epstein-Barr Virus (EBV) transformation of B cells isolated from the peripheral blood of previously infected patients can be performed to develop cell lines which produce naturally occurring human monoclonal antibodies. Preliminary research by the candidate has successfully produced multiple such lines. The primary goals of the proposed research are to: 1. Increase our understanding of the human antibody response to dengue virus infection by creating a library of anti-dengue human monoclonal antibodies;2. Identify which antibodies are neutralizing or enhancing;3. Identify the epitopes that these antibodies target. This research is not only critical to the development of an effective and safe vaccine, but it will also provide a solid foundation for the candidate in the fields of virology and vaccine immunology. It is expected that the candidate will be ready to compete for independent federal funding within two to three years. Several available cores will be utilized to achieve these goals including the genomics, immunology sequencing, statistics and grants and contracts cores.